Help Pineapple RNA extraction

Hi, I am doing RNA extraction for pineapple. I am using acid phenol chloroform method and I am using Amresco phenol chloroform 5 : 1. The company stated that the pH is 4.3 - 4.7 but I always get gDNA contamination every I do the extraction. I don't know what the problem. Can somebody help me to figure it out ? I also want to ask whether the phenol chloroform need to be mixed every time we want to use it. Thank you very much.